Journal of Agriculture and Rural Development in the Tropics and Subtropics Vol. 117 No. 1 (2016) 125–135 urn:nbn:de:hebis:34-2016030349953 ISSN: 2363-6033 (online); 1612-9830 (print) – website: www.jarts.info

Meat yield and quality of Shorthorn Zebu cattle finished on molasses/maize grain with agro-processing by-products in 90 days feedlot period

Lovince Asimwe a,∗, Abiliza Kimambo a, Germana Laswai a, Louis Mtenga a, Martin Weisbjerg b, Jorgen Madsen c, John Safari d

aDepartment of Animal Science and Production, Sokoine University of Agriculture, Morogoro, Tanzania bDepartment of Animal Science, AU Foulum, Aarhus University, Tjele, Denmark cDepartment of Larger Animal Sciences, University of Copenhagen, Frederiksberg, Denmark dInstitute of Rural Development Planning, Dodoma, Tanzania

Abstract

This study was conducted to evaluate the effects of feeding molasses or maize grain with agro-processing by-products on yield and quality of meat from Tanzania shorthorn zebu (TSZ) cattle. Forty five steers aged 2.5 to 3.0 years with 200 ± 5.4 kg body weight were allocated into five dietary treatments namely hominy feed with molasses (HFMO), rice polishing with molasses (RPMO), hominy feed with maize meal (HFMM), rice polishing with maize meal (RPMM) and maize meal with molasses (MMMO). Ad libitum amount of each dietary treatment and hay were offered to nine steers for 90 days. Cooking loss (CL) and Warner Bratzler shear force (WBSF) values were determined on M. longis- simus thoracis et lumborum aged for 3, 6, 9 and 12 days. Steers fed on HFMO diet had higher (P < 0.05) nutrient intake (86.39 MJ/d energy; 867 g/d CP), weight gain (919 g/d) and half carcass weight (75.8 kg) than those fed other diets. Meat of steers from all diets was tender with average WBSF values of 47.9 N cm −2. The CL (22.0 ± 0.61 %) and WBSF (53.4 ± 0.70 N cm−2) were highest in meat aged for 3 days followed by 6, 9 and 12 days. WBSF values for meat aged for 9 and 12 days from steers fed HFMO and RPMM diets were similar and lower than those on other dietary treatments × aging periods. Overall, molasses and hominy feed can be used to replace maize meal in feedlot finishing diets to spare its use in animal feeds. Keywords: agro-processing by-products, feedlot, retail cuts, steers

1 Introduction extrinsic factors (Mushi et al., 2009; Safari, 2010). In Tanzania, meat is mainly produced from Tanzania short- Meat quality is a complex parameter with varying horn zebu (TSZ) cattle which are extensively managed properties and is influenced by several intrinsic and ex- on range lands. In most of these range lands, pastures trinsic factors. The intrinsic factors include breed, sex, are in short supply with low nutritive values especially and slaughter weight, whereas pre- and post-slaughter during the dry seasons resulting in low animal growth carcass handling, type and feeding level are some of the rates, and late attainment of slaughter weights. Stud-

∗ ies have reported loss in weight leading to poor body Corresponding author ff ff Department of Animal Science and Production, Sokoine University condition which a ects meat yield (du Plessis & Ho - of Agriculture, P.O. Box 3004, Morogoro, Tanzania man, 2004) and quality (Muchenje et al., 2008). The Email: [email protected] Phone: +255 713 468 33 constraint of poor nutrition in beef production could

Published online: April 26, 2016 Open access article licensed under a Creative Commons Attribution 4.0 International License CC BY http://creativecommons.org/licenses/by/4.0 126 L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135 be minimised by finishing animals in feedlot using di- assessed for health and nutritional status prior to the ex- ets based on agro-processing by-products. Rice polish- periment to minimise variation errors. Five concentrate ing and hominy feed are agro-processing by-products diets were formulated from different proportions of the that can substitute part of maize grain in concentrate raw materials of the agro-processing by products to con- feed for beef cattle (Matz, 1991). A study by Sani tain hominy feed with molasses (HFMO), rice polishing et al. (2014) on Bunaji bulls fed rice offal as energy with molasses (RPMO), hominy feed with maize meal source showed rice offal to yield high quality carcass (HFMM), rice polishing with maize meal (RPMM) and with lean meat (less amount of fat) compared to maize a control maize meal with molasses (MMMO). The pro- offal. Rice polishing and hominy feed have been found portions of the ingredients composition shown in Table to give consistent results when combined with molasses 1 were determined by trial and error method using nu- and urea (Lopez & Preston, 1977; Larson et al., 1993). tritive values of ingredients from feedstuff tables for ru- A study by Hunter (2012) on beef cattle found that in- minants developed by Doto et al. (2004). Each for- clusion of sugar cane molasses in feedlot diets has the mulated diet was fed together with hay ad libitum to 9 potential of producing meat with good eating quality. steers for a period of 90 days. All animals were provided Earlier study in Tanzania by Mwilawa (2012) on beef with free access of fresh drinking water throughout the fattening using maize meal and molasses has shown experiment and were housed in individual pens. Dur- that TSZ cattle responds well to fattening by increas- ing the experimental period, all animals were weighed ing carcass quantity from 90 kg for sole grazing group after every two weeks and the amount of feed eaten to 154 kg for maize meal and molasses fed group. was weighed daily. The amount of consumed com- Similarly, the quality of meat was improved from 60 pounded diet was 6.20 kg DM/day for MMMO, 6.91 kg Ncm−2 in the sole grazing group to 45 N cm−2 for DM/day for HFMO, 7.05 kg DM/day for RPMO, 5.29 maize meal and molasses fed group. However, the ma- kg DM/day for HFMM and 6.18 kg DM/day for RPMM jor limitation of using maize meal as cattle diet in Tan- diet while the consumed hay was 1.20 kg DM/day for zania is the role it plays as the main food source for MMMO, 1.15 kg DM/day for HFMO, 1.24 kg DM/day humans. Thus, it is of interest to find out alternat- for RPMO, 1.31 kg DM/day for HFMM and 1.32 kg ives to maize meal as feedlot diet which is less com- DM/day for RPMM diet. The metabolisable energy petitive to humans’ food. The available by-product (ME) content of hay was 4.8 MJ/kg DM while the crude feeds that could be used for finishing cattle under feed- protein (CP) content was 33 g/kg DM. The ME contents lot at national level were estimated to be (tones DM) of compounded feeds were estimated using the equation maize bran (5.6 × 105), rice-polishing (8.9 × 104), cot- by MAFF (1975), that was ME (MJ/kg DM) = 0.012 ton seedcake (6.2 × 104), wheat-bran (1.4 × 104), sun- CP + 0.031 EE + 0.005 CF + 0.014 NFE, whereas that flower seedcake (2.1 × 104), wheat-pollard (4.2 × 103) of hay was determined by the McDonald et al. (2002) and molasses (4.5 × 104) (Nandonde, 2008). We hy- equation: ME (MJ/kg DM) = 0.016 DOMD, where pothesize that molasses with other agro-processing by- DOMD = g digestible organic matter per kg dry mat- products can substitute maize meal in feedlot diets ter. without reducing meat yield and quality. Therefore, the objective of this study was to assess the yield and quality 2.2 Slaughter procedures of meat produced from TSZ cattle finished on molasses After 90 days of feeding, all animals were weighed or maize meal with agro-processing by-products under for three days consecutively to obtain the final body feedlot conditions. weight and transported by truck to Dodoma Abattoir (82 km from Kongwa ranch). At the abattoir, the animals 2 Materials and methods were deprived of feed for 24 hours, but had access to fresh drinking water. Slaughtering and dressing of the 2.1 Animals and diets animals followed the abattoir procedures as described A total of 45 TSZ steers aged 2.5–3.0 years with ini- by Bourguet et al. (2011). The animals were stunned us- tial body weight 200 ± 5.4 kg (mean ± SEM) were alloc- ing electrical stunner, slaughtered and suspended on an ated in a completely randomised design to feedlot exper- overhead rail system for bleeding, de-hiding and evis- iment performed at Kongwa ranch, located in Dodoma ceration. The head was removed at the atlanto-occipital region, central Tanzania. These animals were grazing joint, the forefeet and hind feet were removed at the on pastures available at the ranch area for back ground- carpal–metacarpal and tarsal–metatarsal joints, respect- ing before starting the experiment. Animals were also ively. The dressed carcasses were halved into two us- L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135 127

Table 1: Ingredient composition (kg/100 kg), Crude protein (g/kg DM) and Metabolisable energy (MJ/kg DM) levels of the dietary treatments

Compounded diets Ingredients MMMO HFMO RPMO HFMM RPMM

Ingredient composition (kg/100 kg as fed) Maize meal 38 – – 38 38 Hominy feed – 40 – 50 – Rice polishing – – 41 – 51 Molasses 47 47 47 – – Cotton seed cake 13 11 10 10 09 Mineral mix 1 1 1 1 1 Urea 0.5 0.5 0.5 0.5 0.5 Salt 0.5 0.5 0.5 0.5 0.5 Nutritive values Crude protein (g/kg DM) 122 120 97 145 111 Metabolisable energy (MJ/kg DM) 11.0 11.7 10.1 12.6 10.2

MMMO: maize meal with molasses; HFMO: hominy feed with molasses; RPMO: rice polishing with molasses; HFMM homing feed with maize meal; RPMM rice polishing with maize meal.

ing an electrical saw, weighed within 45 minutes post- hind quarters were grouped as prime and nonprime cuts mortem to obtain the hot carcass weight. Temperature based on guidelines issued by VETA (2006). The prime and pH measurements were recorded after 45 minutes cuts comprised the following cuts: shoulder blade, loin and 6 hours post-mortem at room temperature then car- strip, prime ribs, rump, wing ribs, topside, silverside, casses were transferred to a cold room set at 0°C where thick flank and fillet. The nonprime cuts included fore further measurements after 24 hours and 48 hours were and hind shin, hump, neck, flat ribs, chuck, brisket, and recorded. thin flank.

2.3 Fabrication of retail cuts 2.4 Meat quality measurements Twenty five (25) right half carcasses (five carcasses from each treatment (5*5)) were randomly selected from the total of 45 TSZ steers for retail cuts fabrica- 2.4.1 Temperature and pH measurements tion. After 48 hours in a chilling room set at 0°C, the Temperature and pH of the carcasses were taken at 45 carcasses were weighed to obtain cold carcass weight min, 6, 24 and 48 hours post-mortem at the same point and then quartered between 10th and 11th ribs into fore on the 10th rib of left side carcass in the M. longissimus and hind quarters. After recording the weights, the hind thoracis et lumborum (LL). The temperature was meas- quarters were fabricated into nine bone-in retail cuts as ured by inserting a digital meat thermometer (FUNKO- described by FAO (1991), the cuts were hind shin, top- TION Digital stegetermometer, HA 250K, Japan), while side, silverside, fillet, rump, loin strip, thin flank, wing the pH was measured by inserting an electrode (Mettler ribs and thick flank. All visible fat were trimmed and Toledo) of a portable pH-meter (Knickportamess 911, similar procedure was carried out with the fore quar- Germany) in the same muscle. The temperature and pH ters, which were fabricated into eight bone-in retail cuts readings at 45 min and 6 hours post-mortem were taken as brisket, prime ribs, hump, flat ribs, chuck, shoulder at room temperature while temperature and pH readings blade, neck and fore shin. The weight of each individual at 24 and 48 hours post-mortem were taken when the cut was recorded. The retail cuts from the fore and carcasses were in the chilling room. 128 L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135

2.4.2 Determination of cooking loss (CL) and Warner- cutting seven cubes measuring 1×1×1 cm, 5 cm long in Bratzler shear force (WBSF) fibre direction. Warner Bratzler shear blade attached / At the abattoir the LL muscle from 7th to 13th rib of to Zwick Roell (Z2.5, Germany) instrument was used −2 the left side carcass was removed 48 hours post-mortem to determine the force (N cm ) required for shearing and prepared for cooking loss (CL) and Warner-Bratzler through a muscle cube at a right angle to the muscle shear force (WBSF) determination. The LL muscle was fibre direction. The Zwick was set with 1 kN load cell −1 cut into 4 pieces measuring approximately 9 cm long with a crosshead speed of 100 mm min . which were labelled and placed in the chilling room set at 0°C for ageing for 3, 6, 9 and 12 days. After each age- ing time the samples were taken from the chilling room, 2.5 Statistical analysis vacuum packed in polythene bags and frozen at –20°C in a deep freezer. Thereafter the samples were trans- In data analysis, individual animal was considered as ported to the laboratory at the Department of Animal experimental unit in all the variables analysed and initial Science and Production of Sokoine University of Agri- weight was used as covariate. Contrast statements were culture, where CL and WBSF values were determined. used to compare molasses vs maize meal and hominy The LL muscle samples were thawed at 4°C overnight, feed vs rice polishing. The GLM procedure of SAS (ver- removed from the polythene bags, wiped up with pa- sion 9.3, 2002) was used to analyse the data on yield, per towel trimmed down to reduce the size to approx with dietary treatment as the main effect. The differ- mean weight (W1) of 298 ± 36 g and then re-sealed us- ences were considered significant at P < 0.05 and least ing a vacuum pack machine. The samples were heated squares means were separated by LSD. For meat qual- at 75°C for 1 hour in a thermostatically controlled water ity parameters (CL, WBSF, pH and temperature) diet- bath. The heated samples were left to cool under run- ary treatments, time and their interactions were regarded ning tap water for 2 hours, and then transferred to a re- as fixed effects. The MIXED procedure of SAS (Ver- frigerator set at 4°C and stored overnight. The samples sion 9.3, 2002) was used with repeated statement where were removed from the polythene bags, dried with pa- compound symmetry was used as covariance structure. per towel and re-weighed (W2). CL was calculated as Differences were considered significant at P < 0.05 and ((W1 − W2)/W1) ∗ 100. Muscle sample for WBSF as- least squares means were separated by Turkey-Kramer sessment were prepared from the cooked samples by protection.

Table 2: Performance of Tanzania Shorthorn Zebu steers fed molasses or maize meal with rice or maize by-products

Diets P-contrasts Parameters SEM P-values MMMO HFMO RPMO HFMM RPMM MO-MM HF-RP

Initial live weight (kg) 198 203 199 198 203 5.37 0.9253 0.8937 0.9263 Final live weight(kg) 259 c 283 a 264 bc 271 b 258 c 4.12 0.0005 0.0368 0.0003 Average daily gain (g) 658 c 919 a 709 bc 791 ab 639 c 0.05 0.0005 0.0368 0.0003 ME intake (MJ /day) 73.89 b 86.39 a 77.18 b 72.83 b 69.38 b 2.76 0.0013 0.0004 0.0264 CP intake (g/day) 795 b 867 a 725 b 809 ab 737 b 29.6 0.0095 0.421 0.0007 Hot half carcass weight (kg) 69.2 b 75.8 a 68.0 b 69.9 b 65.8 b 1.70 0.0052 0.0339 0.0021 Cold half carcass weight (kg) 67.4 b 74.4 a 66.2 b 68.1 b 64.1 b 1.70 0.0062 0.0314 0.0019 Chilling shrinkage (%) 2.63 1.93 2.61 2.49 2.55 0.45 0.7872 0.6030 0.4136

abc Least squares means with a common superscript in the same raw are not significantly different (P>0.05); SEM, Standard error of the mean; MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal, and RPMM, rice polishing with maize meal; MO-MM, molasses versus maize meal; HF-RP, hominy feed versus rice polishing. L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135 129

3 Results 3.2 Meat quality attributes

3.1 Carcass yield 3.2.1 Temperature and pH The dietary treatments had no effects on the rate of Steers from different dietary treatments differed (P < carcass temperature decline post-mortem (Table 5). The 0.05) in CP and ME intake, growth rate, final live weight decline in temperature was faster in the first 6–24 hours and carcass yield. Steers fed on HFMO diet had higher after which very little change was observed. No dif- (P < 0.05) values than their counterparts from other di- ference (P > 0.05) was observed between dietary treat- ets (Table 2). There was a positive correlation between ments on post-mortem muscle pH decline, but there was growth rate and final live weight (r = 0.99) and between a sharp decline in pH values in the first six hours fol- growth rate and hot/cold carcass weight (r = 0.89). The lowed by a gradual decrease till ultimate pH (pHu) was tendency of dietary treatments to give high values ob- attained at 24 hours post-mortem (Table 5). served on carcass weight was similar to that observed in trimmed fat weight as proportion of half carcass. It was observed that the amount of trimmed fat increased 3.2.2 Cooking loss (CL) and Warner-Bratzler shear with increase in growth rates. At the highest growth rate force (WBSF) (919 g/day) for HFMO steers the amount of trimmed The CL and WBSF values of M. longissimus thoracis fat exceeded that of the lowest growth rate (639 g/day) et lumborum (LL) were not (P > 0.05) influenced by di- for RPMM steers by 65 %. When expressed as propor- etary treatments, but were affected (P < 0.05) by ageing tion of half carcass weight, hind and fore quarter weight, time (Table 6). Higher (P < 0.05) CL and WBSF values saleable cuts, prime and non-prime cuts did not differ were observed on muscle aged for 3 days compared to (P > 0.05) between dietary treatments despite the dif- muscles aged for 6, 9 and 12 days. The lowest values ferences in half carcass weight (Table 3). Dietary treat- for both CL and WBSF were observed on meat aged for ments had no effects (P>0.05) on yield of retail cuts as 9 and 12 days. An interaction (P < 0.05) between di- proportion of side carcass weight (Table 4). When com- etary treatments and muscle ageing time was observed parisons were made between the diets, it was observed for WBSF values. The meat from steers fed HFMO and that molasses and hominy feed based diets had higher RPMM diets and aged for 9 and 12 days had the low- performance than maize meal and rice polishing based est WBSF values compared to those from other dietary diets in all the parameters measured. treatments × aging times (Table 7).

Table 3: Carcass yield from Tanzania Shorthorn Zebu steers fed molasses or maize meal with rice or maize by-products

Diets P-contrasts Parameters SEM P-values MMMO HFMO RPMO HFMM RPMM MO-MM HF-RP

Carcass yield (% side carcass weight): Fore quarter 47.5 48.3 47.8 47.8 46.9 0.87 0.8499 0.4523 0.4015 Hind quarter 49.9 50.0 49.6 49.7 50.6 0.75 0.9418 0.5689 0.6220 Saleable cuts 87.1 85.7 88.5 88.0 87.7 1.20 0.5619 0.5718 0.2897 Prime cuts 46.7 46.4 45.2 46.5 47.6 1.13 0.8286 0.3008 0.9482 Non-prime cuts 40.4 39.3 43.3 41.4 40.1 1.34 0.4659 0.6978 0.3215 Aitch bone 3.08 3.29 3.47 3.12 3.47 0.28 0.7790 0.7927 0.3532 Fat trimmings 4.33 b 6.36 a 4.18 b 4.09 b 3.84 b 0.59 0.0394 0.0487 0.0488 Waste trimmings 2.50 2.42 1.36 1.99 2.56 0.43 0.4882 0.4112 0.5755 Uncountable loss 0.39 0.29 0.26 0.39 0.12 0.30 0.9689 0.9507 0.6208

ab Least squares means with a common superscript in the same raw are not significantly different (P>0.05); SEM, Standard error of the mean; MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal, and RPMM, rice polishing with maize meal; MO-MM, molasses versus maize meal; HF-RP, hominy feed versus rice polishing. 130 L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135

Table 4: Yield of retail cuts from Tanzania Shorthorn Zebu steers fed molasses or maize meal with rice or maize by-products

Diets P-contrasts Parameters SEM P-values MMMO HFMO RPMO HFMM RPMM MO-MM HF-RP

Prime cuts (% side carcass weight): Shoulder blade 9.60 9.50 8.60 9.60 9.20 0.90 0.9261 0.6869 0.5016 Prime ribs 5.33 5.56 5.93 5.86 5.97 0.40 0.6814 0.6720 0.5082 Wing ribs 2.02 2.44 1.95 1.95 2.05 0.36 0.8007 0.5638 0.5406 Loin strip 7.99 7.99 7.40 8.11 8.90 0.49 0.5435 0.1328 0.8366 Rump 4.02 3.99 3.70 3.58 4.85 0.34 0.2593 0.2934 0.1465 Topside 6.13 6.53 6.24 6.38 6.30 0.23 0.6763 0.8206 0.3606 Silverside 6.36 5.62 6.56 5.99 5.51 0.31 0.1322 0.2536 0.4025 Thick flank 4.25 3.90 3.72 4.28 3.88 0.33 0.5729 0.3919 0.3209 Fillet 0.90 0.94 1.07 0.83 0.89 0.13 0.7032 0.2561 0.3995 Non-prime cuts (% of side carcass weight) Fore shine 5.85 5.15 6.78 6.15 5.76 0.93 0.7981 0.9930 0.4458 Hump 2.17 1.79 1.72 2.31 2.30 0.21 0.2103 0.0252 0.8562 Neck 6.58 6.41 6.72 6.80 6.27 0.42 0.9454 0.9434 0.7904 Chuck 4.92 5.17 5.06 5.12 5.59 0.49 0.8979 0.6166 0.6873 Flat ribs 4.25 4.05 4.15 4.21 4.01 0.34 0.9881 0.9710 0.8958 Brisket 7.87 8.20 7.69 7.35 7.09 0.43 0.2896 0.0840 0.3100 Thin flank 3.95 4.50 6.38 4.84 4.51 0.71 0.1901 0.2566 0.2204 Hind shine 4.80 4.01 4.83 4.65 4.54 0.24 0.0920 0.4534 0.1032

SEM, Standard error of the mean; MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal, and RPMM, rice polishing with maize meal; MO-MM, molasses versus maize meal; HF-RP, hominy feed versus rice polishing.

Table 5: Effect of time change on temperature decline and pH change post-mortem for five dietary treatments

Variables Dietary treatments 45 min 6 (hrs) 24 (hrs) 48 (hrs)

Temp pH Temp pH Temp pH Temp pH

MMMO 35.7 6.46 26.2 5.88 1.4 5.62 1.1 5.52 HFMO 37.0 6.36 27.0 5.87 1.5 5.67 1.1 5.56 RPMO 36.0 6.41 26.1 5.84 1.2 5.71 1.0 5.52 HFMM 36.6 6.43 26.6 5.95 1.4 5.69 1.2 5.51 RPMM 35.8 6.30 26.3 5.86 1.0 5.63 0.8 5.50

SE 0.37 0.04 0.37 0.04 0.37 0.04 0.37 0.04 P-value 0.7973 0.4313 0.7973 0.4313 0.7973 0.4313 0.7973 0.4313

SE, Standard error of the mean; MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal and RPMM, rice polishing with maize meal; MO-MM, molasses versus maize meal; HF-RP, hominy feed versus rice polishing. L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135 131

Table 6: Cooking losses and Warner-Bratzler shear force values for Tanzania Shorthorn Zebu steers fed molasses or maize meal with rice or maize by-products

Cooking loss (%) Shear force (N cm−2)

Dietary treatments (T) MMMO 21.5 49.0 HFMO 21.0 46.4 RPMO 20.3 50.8 HFMM 19.6 49.4 RPMM 19.7 44.0 SEM 0.82 3.72 P-value 0.42 0.72

Ageing (A, days) 3 22.0 b 53.4 c 6 20.3 a 48.7 b 9 20.1 a 45.1 a 12 19.3 a 44.3 a SEM 0.61 1.70 P-value 0.01 <0.0001 T × A 0.18 <0.0001 P-contrasts (MO-MM) 0.24 0.61 P-contrasts (HF-RP) 0.75 0.89

abc Least squares means with a common superscript in the same raw are not significantly different (P>0.05); SEM, Standard error of the mean; MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal and RPMM, rice polishing with maize meal; MO-MM, molasses versus maize meal; HF-RP, hominy feed versus rice polishing.

Table 7: Effect of ageing time on tenderness for the five dietary treatments (N cm−2)

Dietary treatments

Ageing time MMMO HFMO RPMO HFMM RPMM Mean

3 days 53.4 a±3.5 56.3 a±1.2 54.1 a±1.2 53.9 a±1.2 50.1 a±1.2 53.5±0.6 6 days 50.9 a±3.5 47.4 b±1.2 50.3 a±1.2 50.3 ab±1.2 43.0 bc±1.2 48.4±0.6 9 days 50.0 a±3.5 40.6 c±1.2 50.0 b±1.2 44.5 a±1.2 40.8 c±1.2 45.2±0.6 12 days 44.3 b±3.5 40.5 c±1.2 48.8 b±1.2 44.5 b±1.2 40.6 b±1.2 44.3±0.6 Mean 49.0±3.4 46.4±0.7 50.8±0.7 49.4±0.7 44.0±0.7

P-values for main effects: Dietary treatments, 0.72; Ageing time, 0.61;abc Least squares means with a common superscript in the same column are not significantly different (P>0.05); MMMO, maize meal with molasses; HFMO, hominy feed with molasses; RPMO, rice polishing with molasses; HFMM, hominy feed with maize meal and RPMM, rice polishing with maize meal. 132 L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135

4 Discussion 4.2 Meat quality attributes

4.2.1 Temperature and pH 4.1 Carcass yield The rate and extent of decline of muscle pH and tem- perature during the immediate post-mortem periods ser- The observed higher final body weight and carcass iously influence meat quality development, mainly ten- weight for steers fed HFMO diet compared to those fed derness (Safari, 2010; Frylinck et al., 2013), because other diets could be associated with high intake levels temperature changes can initiate cold or heat shortening. of both energy and protein nutrients. Likewise, steers A rapid decline in temperature during early post-mortem fed HFMO diet had the highest level of fat deposition when muscle pH is still high can cause cold shortening (highest amount of trimmed fat). Growth rate and fat (Frylinck et al., 2013), which will lead to tough meat. deposition are directly related with the level of energy In the present study, pH reading reached 6 while the and protein intake as they increase muscle and fat mass temperature was still high (>26.5°C) which shows unfa- (Safari, 2010; Khalid et al., 2012). These findings co- vourable conditions for cold shortening to occur. Lack incide with observations by Pazdiora et al. (2013) who of dietary effect on pH values for concentrate fed cattle found the degree of fat cover to increase with the body observed in the present study is in agreement with find- weight of animals. Part of high final weights observed ings from other studies (Mapiye et al., 2010; Lage et al., could be due to compensatory growth, which is com- 2012). The findings indicate that there was sufficient monly seen for old animals of this age given ad lib- glycogen content in the muscles of animals in these dif- itum access to feed following a period of restricted feed- ferent dietary treatments. The average pH of 5.67 for ing, since these animals were grazing on poor range carcasses in the present study is within the quality range land pasture before they were taken in feedlot. The ob- of 5.5 to 5.8 which is considered normal and optimal ac- served increased amount of trimmed fat was found to cording to shelf life and eating properties (Silva et al., decrease the amount of saleable cuts. This implies eco- 1999; Mach et al., 2008). nomic losses to beef producers, since excess fat deposits are not part of usable carcass under certain market con- 4.2.2 Cooking loss and Warner-Bratzler shear force ditions (Kitts, 2011). It is however, important to note Cooking loss in muscles depend on ultimate pH, that preference for fat content varies with place and cul- cooking conditions (Mushi et al., 2009), and intramus- ture. For instance, Kamugisha (2014) reported that con- cular fat content (Safari, 2010). Although intramuscu- sumers in Arusha, Tanzania showed high preference to lar fat content was not measured in the present study, it meat with high fat content which suggests the need for can be argued that the magnitude of pH variation was taking into account preferences of targeted consumers not large enough to elicit differences in CL values. The in feedlot finishing. values observed for CL are comparable to the range of The observed chilling shrinkage of 2.4 % in the 16.8 to 24.6 % reported by Mwilawa (2012) on TSZ present study was comparable to the range of 2.4–2.7 % steers fed 100 % concentrate, but are slightly lower than observed by Khalafalla et al. (2011) and Fadol & the 22.5 to 25.2 % reported by Mapiye et al. (2010) on Babiker (2010) in Baggra bulls, and is slightly Nguni steers. This deviation may be attributed to differ- above the standard cold shrinkage of 2.0 % in 24 hours ences in feeding systems, breeds and ageing time used chilling (Pascoal et al., 2010). The absence of dietary between studies. The observed WBSF values are within ff ff e ects on yield of di erent retail cuts including primal the range of 41.8 to 50.9 N cm−2 reported on carcases of ff and non-primal cuts suggests that di erences in levels TSZ steers fed concentrate diet with 125 g CP and 12 of dietary energy and protein in the present study were MJ ME per kg DM (Mwilawa, 2012). Lack of dietary ff not large enough to elucidate di erences in yield of effects on CL and WBSF concurs with previous studies retail cuts. Similar findings have been observed in (Lage et al., 2012; Neto et al., 2012). several other studies involving beef cattle (Fadol & Meat samples from carcasses from cattle in the five Babiker, 2010; de Souza Duarte et al., 2011; Turki treatments in the current study are considered tender as et al., 2011). On the other hand, studies have shown that WBSF values are less than 50 N cm−2 (Devitt et al., variation in terms of breed (Sharaf Eldin et al., 2013), 2002). The lowest values for CL and WBSF observed sex (Lazzaroni & Biagini, 2008) and age (Pazdiora on meat aged for longer days (9 and 12 days) may be et al., 2013) of animals has significant effects on the associated with enzymatic reactions that disintegrate the distribution of cuts. myofibrillar proteins with increasing ageing time. The influence of ageing time on CL and WBSF has also L. Asimwe et al. / J. Agr. Rural Develop. Trop. Subtrop. 117 - 1 (2016) 125–135 133 been observed in previous studies (Florek et al., 2009; Doto, S. P., Kimambo, A. E., Mgheni, D. M., Mtenga, Filipcíkˇ et al., 2009). L. A., Laswai, G. H., Kurwijila, L. R., Pereka, A. E., In general, post-mortem storage resulted in decreased Kombe, R. A., Weisbjerg, M. R., Hvelplund, T., Mad- CL and WBSF values. Observations from this study sen, J. & Petersen, P. H. (2004). Tanzania feedstuff have shown that dietary treatment and ageing time are table for ruminants. Sokoine University of Agricul- two factors that independently affect meat quality char- ture, Morogoro, Tanzania. 71pp. acteristics of steers but jointly influenced the WBSF val- Fadol, S. R. & Babiker, S. A. (2010). Effect of feed- ues which decreased most for HFMO and RPMM di- lot regimen on performance and carcass characterist- th th ets on 9 and 12 days of ageing. Ageing increases ics of Sudan Baggara Zebu cattle. Journal of Live- tenderisation by degrading and weakening structural in- stock Research for Rural Development, 22, Article tegrity of myofibrillar proteins brought by the calpain #27. URL http://www.lrrd.org/lrrd22/2/ µ proteolytic enzyme system especially -calpain (Safari, fado22027.htm (last accessed: 10.05.2012). 2010; Kemp & Parr, 2012). On the other hand, energy concentration consumed by the animal influences gly- FAO (1991). Guideline for slaughtering, meat cut- cogen stores which decrease ultimate muscle pH, and ting and further processing. FAO Animal Pro- thus influencing meat tenderness. The influence of con- duction and Health Paper 91, Food and Ag- sumed energy on glycogen reserve has also been repor- riculture Organization of United Nation, Rome, ted by Koger et al. (2010). In addition, high energy di- Italy. URL http://www.fao.org/docrep/004/ ets influences tenderness by increasing intramuscular fat t0279e/T0279E00.htm (last accessed: 09.2011). that gives rise to the dilution of muscle structure (Wood Filipcík,ˇ R., Šubrt, J. & Bjelka, M. (2009). The factors et al., 1999; Cardeno et al., 2006). It can be concluded influencing beef quality in bulls, heifers and steers. that molasses with hominy feed can substitute maize Slovak Journal of Animal Science, 42, 54–61. meal in feedlot diets without reducing meat yield and quality of TSZ cattle finished in feedlots in 90-days feed Florek, M., Litwinczuk,´ Z. & Skałecki, P. (2009). In- lot period. fluence of slaughter season of calves and ageing time on meat quality. Polish Journal of Food and Nutrition Science, 59, 309–314. Acknowledgements Authors are grateful to the financial support provided Frylinck, L., Strydom, P. E., Webb, E. C. & du Toit, E. ff by the SUA-IGMAFU project and positive collaboration (2013). 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